This invention relates to a wiper blade assembly and more particularly to a wiper blade pressure distributing yoke provided with means to enable it to be coupled to a wiper arm having a pivot pin of the side mounting type. Primarily the invention is concerned with wiper blade assemblies for vehicle windshields or windscreens but it may also find application for use with vehicle headlamps.
Wiper arms of the side mounting type have a transversely extending pivot pin protruding from one side. In use the pivot pin is inserted into a transverse socket formed in a main yoke of a wiper blade assembly and conventionally is detachably held in position within the socket by some form of latching device cooperating with an annular recess formed in, and spaced from a free end of, the pivot pin.
One known type of wiper blade assembly is disclosed in U.S. Pat. No. 4,503,580. In this known specification, the wiper blade assembly includes a primary yoke having a rigid central portion in which is formed a transverse pivot pin receiving socket extending from one to the other side of the central portion. A plastics latching member is mounted within a yoke recess which is formed in the underside of the central portion and which opens into the pivot pin receiving socket. The yoke recess extends underneath the pivot pin receiving socket from an upwardly extending yoke pocket to an upwardly extending yoke passageway which opens to the topside of the central portion, the yoke pocket and yoke passageway being disposed on opposite sides of a transverse vertical plane containing the axis of the pivot pin receiving socket. The latching member has at one of its end an anchoring plug consisting of two spaced apart, upwardly extending protrusions which are received within the yoke pocket to retain the latching member in the yoke recess. The latching member further comprises a latching portion resiliently joined to the bottom of the anchoring plug and which is normally received within an annular recess of a wiper arm pivot pin to retain the latter in the pivot pin receiving socket, and a finger depressible actuating member rigidly joined to the latch portion and positioned in, so as to extend to the top of, the yoke passageway and which can be depressed to resiliently move the latch portion relative to the anchor portion and clear of the pivot pin annular recess thereby allowing the pivot pin to be removed from the pivot pin receiving socket. The yoke pocket has a mouth portion leading into a wider chamber thereover. The spaced apart upwardly extending protrusions of the anchoring plug have enlarged heads each provided with a downwardly and outwardly sloped end surface with a ledge thereunder. During connection of the latching member, the anchoring plug is pushed upwardly into the yoke pocket. As the sloping end surfaces of the enlarged heads pass through the mouth portion of the yoke pocket, they are resiliently urged towards each other before springing apart as they enter the wider chamber of the yoke pocket. The ledges of each enlarged head engage against walls of the wider chamber bordering the mouth portion and anchor the latching member in position.
The latching member of the wiper blade assembly described in U.S. Pat. No. 4,503,580 is anchored in position solely by the engagement of the enlarged heads of the upwardly extending anchoring protrusions within the enlarged chamber of the yoke pocket. The yoke pocket and the protrusions have to be manufactured to high tolerances to ensure a tight fit of the anchoring plug in the yoke pocket so that the latching member is securely seated within the yoke recess and does not move to an unwarranted extent; to ensure, for the sake of a good appearance, that the latching member seats flush with the bottom of the central portion of the yoke in normal use; and to ensure that depression of the finger depressible actuating member does not create a sufficiently large downward force and/or turning force on the anchoring plug to cause the latter to become released from its anchored position. Since the latching member is anchored at one end only, any slight play between the anchoring plug and the yoke pocket when the latching member is in its anchored position will be amplified at the position where the latching portion engages with the pivot pin recess in the region of the pivot pin socket.
An alternative proposal for anchoring a latching member within a yoke recess is shown in FIGS. 1 and 2. In this alternative proposal, two latching protrusions are provided. However, instead of these latching protrusions being at one end only of the latching member, they are provided at opposite ends of the latching member with each latching protrusion having an enlarged head which interengages with an outwardly disposed cavity at either end of a yoke recess. A resiliently deflectable latching portion forming an integral part of the latching member is joined to the latter adjacent one of its ends and extends between the opposite ends of the latching member. An upstanding, finger depressible actuating member positioned between the two latching protrusions is integrally joined to the other end of the latching member and is depressible to release the latching portion from engagement with an annular recess of a wiper arm pivot pin.
Such a latching member overcomes many of the problems associated with wiper blade assembly described in U.S. Pat. No. 4,503,580. However there are two additional drawbacks to the design. Firstly, the downward depression of the actuating member causes the base of the latching member to bow downwardly between its ends causing the upper ends of the two latching protrusions to move in towards each other. This results in each of the enlarged heads of the latching protrusions being moved in a direction out of interengagement with its associated outwardly disposed cavity in the yoke recess. In practice the downward pressure on the finger depressible latching member often leads to the disengagement of the latching member from the yoke recess so that the latching member becomes detached from the yoke. Secondly, the length of the yoke recess is less than the length of the latching member between the enlarged heads of the latching protrusions, the upper ends of the latching protrusions containing these enlarged heads therefore have to be resiliently urged or squeezed together during assembly of the wiper blade assembly to ensure that the latching member can be inserted into the yoke recess. The assembly process is therefore made more complicated.